In a 3GPP network, the physical uplink control channel (PUCCH) is used to transmit uplink control information (UCI) from User Equipment (UE) to a 3GPP eNodeB (eNB). An example of the UCI information is an acknowledgement signal in a Hybrid Automatic Repeat reQuest-ACKnowledgement (HARQ-ACK) process. Typically, PUCCH resources are dynamically allocated to a mobile station based upon the lowest carrier control element (CCE) index of a signal transmitted on the PDCCH by the eNB using one or more CCEs. Because the PDCCH transmission is unique to a given UE, use of the CCE index would result in the UE being assigned a unique uplink resource on the PUCCH.
However, an enhanced physical downlink control channel (ePDCCH) using one or more enhanced carrier control elements (eCCEs) has recently been introduced to the 3GPP specifications. The uplink resource of the PUCCH may be based on the lowest eCCE index for one or more eCCEs used for a transmission on the ePDCCH. In certain instances the lowest CCE index and the lowest eCCE index may be in the same. In these instances, an uplink resource allocated to a first UE using the lowest CCE index of the PDCCH may be the same as an uplink resource allocated to a second UE using the lowest eCCE index of the ePDCCH, resulting in a resource allocation collision.
Cell-specific reference signals (CRS) may be transmitted in DL subframes except for multimedia broadcast/multicast service (MBMS) regions in multimedia broadcast/multicast service network (MBSFN) subframes. In a certain carrier, with non-backward compatibility, CRS can be removed or reduced to increase DL throughput as well as to provide network energy saving. Also, legacy PDCCH is not transmitted but PDSCH is scheduled by either ePDCCH or cross-carrier scheduling from legacy cells using legacy PDCCH.
In a heterogeneous network with low power RRHs within the macrocell coverage are, e.g., coordinated multipoint (CoMP) scenario 4, the transmission/reception points created by the RRHs have the same cell IDs as the macro cell. Since the same physical Cell ID is used for several RRHs, the capacity for CRS based PDCCH is limited. This is mainly due to the CRS is transmitted from the RRHs as well as from macro cells in a synchronous or quasi-synchronous manner. Accordingly, enhanced PDCCH has been proposed to address PDCCH capacity.
To reduce overhead and inter-cell interference levels, a new carrier type (NCI) has been introduced. The new carrier type is complementary to legacy carrier type(s) and is backward compatible. For example, ePDCCH may be transmitted on the new carrier type (NCT). However, a resource allocation method has not been developed for ePDCCH transmitted on NCT. Moreover, dynamic resource allocation of HARQ-ACK transmission has not been adequately addressed.